Until the development of copper interconnect technology, copper was not found in wastewater from the production of multilayer microchips by the semiconductor industry. Copper is now being used as a replacement for aluminum and/or tungsten because of its lower electrical resistivity in processes referred to as chemical-mechanical polishing or chemical-mechanical planarization (known as "CMP") and therefore is now being found in wastewater. Copper is an undesirable component of wastewater because of its toxicity to aquatic organisms such as fish and adverse health effects to humans who ingest copper-contaminated drinking water. Thus, copper is regulated in discharges to the environment so it is imperative that viable methods be found to detect and remove copper in wastewater streams from the semiconductor industry.
For purposes of this application, printed circuit boards, also known as printed wiring boards, are defined as "physical structures on which electronic components such as semiconductors and capacitors are mounted". In contrast to the semiconductor industry, copper is usually found in the wastewater from the printed circuit board industry. However, methods to detect and remove copper from the wastewater of the printed circuit board industry have not yet been optimized.
Analytical methods useful to detect copper are described in the following references:
U.S. Pat. No. 5,132,096 claims an on-stream analyzer to determine the concentration of a treating agent added to a body of water, and to determine the presence of an uncompensated stress metal which may be present in spite of the treating agent. The use of an unconsumable transition metal tracer is described with this analyzer.
U.S. Pat. No. 5,278,074 claims a method for controlling the concentration of an aromatic azole corrosion inhibitor in the water of an industrial aqueous system.
U.S. Pat. No. 5,411,889 claims a method of regulating the in-system concentration of a water treatment agent in an industrial fluid system comprising: adding an inert tracer to an industrial fluid system, the inert tracer being added in known proportion to a target specie also being added to said industrial fluid system wherein the system consumption of the target specie is effected by the water treatment agent; drawing a sample of fluid from said industrial fluid system; monitoring the target-specie by analysis of said sample to determine at least one characteristic that can be correlated to an in-system concentration of said target-specie; monitoring said inert tracer by analysis of said sample to determine the in-system concentration of said inert tracer; determining the system consumption of the target specie from the measured in-system concentration of the target specie and the inert tracer; and regulating the in-system concentration of the water treatment agent in the fluid system based on the system consumption of the target specie. Example 3 (Columns 31-32) describes using the process to detect cupric ion (Cu.sup.+2) in a series of synthetic industrial water solutions.
U.S. Pat. No. 3,877,878 discloses an analytical device and a method for monitoring heavy metals in natural waters.
U.S. Pat. No. 3,898,042 discloses a method and apparatus for continuously determining total copper in an aqueous stream.
U.S. Pat. No. 4,908,676 discloses sensors for detecting dissolved substances, including copper, in aqueous fluids.
U.S. Pat. No. 4,400,243 discloses the monitoring of the heavy metal ions silver, cadmium, lead and copper using an electrode system.
U.S. Pat. No. 5,292,423 discloses an apparatus and a method to use the apparatus to analyze trace metals, including copper.
U.S. Pat. No. 5,578,829 discloses a method of monitoring a material flow for a contaminant therein.
German Patent 19512908 discloses a method for analyzing wastewater from galvanizing wastewaters.
Additional references describing detecting methods for copper include the following: Ionics Inc. Instrument Division, "Water Quality Monitoring Guide for Anodic Stripping Voltammetry"; "Industrial Wastewater Treatment Technology", 2.sup.nd Edition, James W. Patterson .COPYRGT.1985 by Butterworth-Heinemann, "Chapter 7-Copper, pp. 91-109; Auyong, "On-Line Monitoring of Toxic Materials in Sewage at the Lawrence Livermore Laboratory", U.S. Environmental Protection Agency, issue EPA-600/9-81-018, 1981; Kubiak and Wang, "Algae Columns with Anodic Stripping Voaltammetric Detection", Anal. Chem., vol. 61, no. 5, Mar. 1, 1989, pp. 468-471; Glass et al., "Electrochemical Array Sensors For Plating Waste Stream Monitoring", Proc. AESF Annu. Tech. Conf., vol. 79, pp. 83-102 (1992); Bratin et al., "On-Line Electrochemical Monitoring of Waste and Rinse Water Streams", Proc. AESF. Annu. Tech. Conf., vol. 82, pp. 755-764 (1995); Vanhumbeek, "Automatic Monitoring of Copper in Waste Water From Plating Shops", Wat. Sci. Tech., Vol. 13, pp.539-544 (1981); Connolly et al., "On-Line Measurement of Sub-PPB Levels of Metals Using X-Ray Fluorescence", Ultrapure Water, vol. 15, pp. 53-58 (1998); Schlager, "On-Line Spectroscopic Monitoring of Metal Ions For Environmental and Space Applications Using Photodiode Array Spectrometry"; Beauchemin et al., "Determination of Trace Metals in Reference Water Standards by Inductively Coupled Plasma Mass Spectrometry with On-Line Preconcentration", Anal. Chem., vol. 61 pp. 1857-1862 (1989); Cnobloch, "Continuous Monitoring of Heavy Metals In Industrial Waste Waters", Analytica Chemica Acta, vol. 114, pp. 303-310 (1980); Product Literature from Environmental Technologies Group, Inc. about "ETG METALYZER.TM. 5000"; Ng et al., "Quartz Crystal Microbalance Sensor Deposited with Langmuir-Blodgett Films of Functionalized Polythiophenes and Application to Heavy Metal Ions Analysis", Langmuir, vol. 14, pp. 1748-1752 (1998); and Groves et al., "Inductively Coupled Plasma Monitoring of Semi-conductor Wastewater", Process Control and Quality, vol. 7, pp. 85-90 (1995).
Methods useful to remove copper from aqueous systems are described in the following references:
U.S. Pat. No. 4,462,913 discloses a process for treating wastewater, produced in wire drawing and rolling, with said wastewater containing fat and heavy metal ions, including copper.
U.S. Pat. No. 5,164,095 discloses dithiocarbamate polymers and use of these polymers in removing heavy metals from water.
U.S. Pat. No. 5,346,627 discloses a method for removing monovalent and divalent metals including copper from a fluid stream using a water soluble ethylene dichloride ammonia polymer having a molecular weight of from 500 to 100,000 that contains from 5 to 50 mole percent of dithiocarbamate salt groups to form complexes with the monovalent and divalent metals.
U.S. Pat. No. 5,328,599 claims a wastewater treatment system and method for chemical precipitation and removal of metals from wastewater in a continuous or batch treatment process which includes an ion-selective electrode and a reference electrode disposed in a precipitation tank for measuring an electrochemical potential therebetween in a predetermined range. A controller unit is provided which is responsive to the electrochemical potential in the predetermined range and is connected to a precipitant feed unit for automatically controlling the chemical precipitant fed into the precipitation unit.
U.S. Pat. No. 5,401,420 claims a method of automatically controlling the chemical feed of an organic sulfide chemical precipitant to a wastewater treatment system. The organic sulfide is selected from the group consisting of dithiocarbamates, trimercaptotriazines, trithiocarbonates and polymeric dithiocarbamates.
U.S. Pat. No. 5,286,464 discloses that lead and cadmium ions are selectively removed and reclaimed from aqueous liquids containing the ions of these metals using an ion exchange resin which comprises a modified silica gel. It claims: in an ion exchange process to selectively remove the metals, lead and cadmium, from aqueous liquids containing the ions of these metals wherein these liquids are contacted with an ion exchange resin for a period of time sufficient for the ion exchange resin to complex with the lead and cadmium ions in the aqueous liquids and then regenerating the resin to remove and recover the metals from the resin; the improvement which comprises using as the ion exchange resin an amorphous silica gel having a surface area of at least 100M.sup.2 /g having at least 10% of its surface silanol groups reacted with a triethoxy silane selected from the group consisting of Bis(2-hydroxyethyl)-3-aminopropyltriethoxysilane and N-[3-(triethoxysilyl)propyl]-4,5-dihydroimidazole.
U.S. Pat. No. 5,552,058 discloses a filtering method for removing particulate matter and dissolved heavy metals from cooling tower water by passing the cooling tower water through a filter assembly containing a particulate matter filter and a heavy metals filter having a filter element having metal particles bound together in a porous sponge like structure.
PCT WO 96/38227 discloses and claims water-soluble polymers for recovery of metals from solids.
Relative size of various common materials used in filtration is described in "The Filtration Spectrum" from Osmonics, Inc., 5951 Clearwater Drive, Minnetonka, Minn. 55343.
Solid-Liquid separation various techniques are described in Chapter 3.1 of the book, "Water Treatment Membrane Processes", edited by Joel Malleviale et al., .COPYRGT.1996 McGraw-Hill, pp. 3.3-3.4, 3.12-3.13, 3.12ISBN 0-07-001559-7. Solid-Liquid separation using ultrafiltration can be found in the same reference at pp. 10.1, 10.12 and 10.8. Solid-Liquid separation using microfiltration can be found in the same reference at pp. 11.1 and 11.3-11.5. Solid-Liquid separation using electrodialysis can be found in the same reference at pp. 12.1-12.10.
Membrane Separation Processes are described in "Membrane Separation Processes", edited by Patrick Meares, .COPYRGT.1976 by Elsevier Scientific Publishing Company, Amsterdam, pp. 512-513. They are also described in "Membrane Handbook", edited by W. S. Winston Ho, .COPYRGT.1992 by Van Norstrand Reinhold, pp. 326-327, 335-336, 348-354.
"Carbon Adsorption Handbook" edited by Cheremisinoff and Ellerbush, .COPYRGT.1978 by Ann Arbor Science Publishers, Inc., describes the removal of copper(II) by activated carbon using synthetic seawater of high ionic strength. Among the six different kinds of activated carbon tested, Barneby-Cheney PC-8592 was the most efficient adsorbent for Cu(II) removal (adsorption). However, the removal efficiency was still very poor with a low 6% (FIGS. 8-10).
What is needed is a method to both detect and remove copper from wastewater process streams from the manufacture of semiconductors and printed circuit boards that is reliable under actual manufacturing conditions. This method must be capable of automation and allow for upsets in process conditions.